This is a very old group of trick taking games - the earliest reference is from 1426. Karnöffel was one of the first games to introduce a kind of trump suit - a suit whose cards had increased power, and were able to beat cards of other suits. It is possible that Karnöffel predated the invention of tarot, though it was from tarot, not Karnöffel, that the idea of a trump suit spread to the majority of European trick-taking games. In Karnöffel games the "trump" suit is properly called the chosen suit. Instead of designating a whole suit as trumps and having it rank in the same order internally as the other suits, the power to beat cards of the other suits was assigned only to certain cards of the chosen suit, and the ranking among these cards was quite different from the ranking in the unchosen suits.
Descendents of this game are still played in Switzerland and in Scandinavia. They can be recognised by the wildly disturbed card order, and the special property of the seven of a chosen suit. A chosen seven cannot win a trick unless it is led, but if a chosen seven is led it cannot be beaten, or can only be beaten by a limited number of specific cards.
The closest modern game to the original Karnöffel is the Swiss Kaiserspiel, also known as Kaiserjass though it is unrelated to Jass games proper.
In the Scandinavian versions the number of chosen suits was increased. Some games had two chosen suits: